1. Field of the Invention
The present invention relates to a display device and a method for driving the display device, and particularly to a display device which comprises a display panel on which there are arranged a plurality of display pixels provided with current control type light emitting elements that emit light at a predetermined luminance gradation by supplying a current responsive to display data, and a method for driving the display device.
2. Description of the Related Art
Conventionally, there has been known a light emission type display (display device) that comprises a display panel on which there are arranged, in a two-dimensional manner, a plurality of display pixels provided with current control type light emitting elements that emit light at a predetermined luminance gradation responsive to a current value of supplied driving current, like organic electroluminescence elements (hereinafter, abbreviated as “organic EL elements) or light emitting diodes (LEDs).
In particular, in a light emitting element type display having applied an active matrix type driving system, a display response speed is fast with no viewing angle dependency in comparison with a liquid crystal display device (LCD) that has been prevalent in recent years. In addition, this light emitting type display enables high luminance or high contrast, high quality and resolution of display image, and low power consumption and is composed of light emitting element type display pixels. Thus, there is no need for backlight unlike the case of the liquid crystal display device. Therefore, the light emitting element type display has a very advantageous feature that it enables further downsizing and reduction in weight or power saving and is actively researched and developed as a next generation display.
FIG. 16 is a schematic view showing an exemplary configuration of essential portions of a light emitting element type display in a conventional technique.
As shown in FIG. 16, the light emitting type display in the conventional technique has a configuration provided with: a display panel 110P on which a plurality of display pixels EMp provided with current control type light emitting elements (for example, organic EL elements) are arranged in a matrix manner in the vicinity of cross points between a plurality of scanning lines (gate signal lines) SLp and a plurality of data lines (source signal lines DLp that are arranged so as to be orthogonal to each other; a scanning driver (gate driver) 120P connected via a contact point NSp to the scanning lines SLp of the display panel 110 and setting (scanning) the display pixels EMp per line in an active state by sequentially applying a scan signal Vsel with a predetermined timing to each of the scanning lines SLp; and a data driver (signal driver circuit) 130P connected via a contact point NDp to the data lines DLp of the display panel 110P and capturing display data (or video data) to supply to each of the data lines DLp, with a predetermined timing, a gradation signal responsive to display data.
In such a display, for example, operating states of the scanning driver 120P and the data driver 130P are controlled based on signals such as a scan control signal and a data control signal supplied from a timing control circuit (such as system controller), although not shown. Then, a gradation signal responsive to display data is written and held in display pixels EMp of each line set at an active state by applying a scan signal Vsel. In this manner, the light emitting elements provided to display pixels EMp are operated to emit light during a predetermined period and at a predetermined luminance gradation, thereby making it possible to achieve an active matrix type driving system for displaying desired image information.
In addition to the light emitting elements (organic EL elements) described above, the configuration for achieving the driving system described above is provided with a pixel driver circuit (or pixel circuit) made of a plurality of switching elements (such as thin film transistors) for controlling light emission by supplying to the light emitting elements a light emitting drive current with a current value responsive to display data for each of the display pixels EMp arranged on the display panel 110P.
Here, as shown in FIG. 16, the above configuration is provided so that the gradation current generated by means of the data driver 130P (a plurality of gradation current generating circuits) is output to each of the data lines DLp arranged on the display panel 110P in a relationship of 1:1 via an individual contact point (connector terminal) NDp. Thus, in the case where high resolution has been achieved by increasing the number of data lines arranged on the display panel, the number of output terminals of the data driver also increases corresponding to the number of data lines. In addition, the number of connector terminals between the data driver and the display panel (panel substrate) provided as driver chips (IC chips) increases. Therefore, there has been a problem that pitches (gaps) between terminals narrow, requiring high precision of alignment in a process for connecting the driver chips and an increased number of man-days or the like, resulting in higher manufacturing costs.